Contact lenses (to be referred to as "CL" hereinafter) are roughly divided into hard contact lenses (to be referred to as "HCL" hereinafter) and soft contact lenses (to be referred to as "SCL" hereinafter) depending on the flexibility of raw materials. The conventional HCL raw materials cannot be applied to continuous wearing for a prolonged period of time because of their impermeability of oxygen which is necessary for the metabolism of corneal tissues. Hence, raw materials having high oxygen permeability have been developed and are now popularly applied to continuously wearable HCL having high oxygen permeability. With regard to the raw materials of SCL, on the other hand, hydrous high polymers having high oxygen permeability have been used and are now popularly applied to continuously wearable highly hydrous SCL. However, since the contact time of the CL material with ophthalmic tissues such as cornea, conjunctiva and the like becomes long as the continuous wearing of CL is prolonged, it has been desired to develop a material having more high tissue compatibility (biocompatibility with ophthalmic tissues).
Collagen has been known as a CL material having tissue compatibility (JP-B 62-42487, U.S. Pat. No. 4,223,984, U.S. Pat. No. 4,260,228, U.S. Pat. No. 4,264,155) and commercialized as Collagen Lens (Bausch & Lomb, U.S.A.) (the term "JP-B" as used herein means an "examined Japanese patent publication"). Also, JP-B 62-42487 discloses a CL which is formed after mixing collagen with a chondroitin sulfate or the like mucopolysaccharide (glycosaminoglycan). However, collagen, which is a protein, has a disadvantage of having antigenicity. The eye is highly sensitive especially against exogeneous material and apt to cause inflammations when the exogeneous material has antigenicity.
In addition, various raw materials of the CL and the like materials to be worn on the eyeball have been known, such as a raw material which comprises a polyvinyl alcohol-based gel containing a chondroitin sulfate or the like acid polysaccharide (JP-B 51-11139), chitin or chitosan (JP-A 56-94322, JP-W 61-501729, JP-A 63-50816, JP-A 4-176459, JP-A 4-275346 and the like), glucomannan (JP-A 5-163384), silk fibroin (JP-A 5-313105) and the like (the term "JP-A" as used herein means an "unexamined published Japanese patent application", and the term "JP-W" as used herein means an "unexamined published Japanese international patent application"). However, all of such raw materials have a problem in terms of tissue compatibility, because their principal components do not originate from biological materials(vertebrate).
As described above, raw CL materials which contain glycosaminoglycan are known, but no CL which substantially comprises glycosaminoglycan alone.
An object of the present invention is to provide materials to be worn on the eyeball having a semi-spherical shape, such as contact lenses for use in the visual acuity correction or medical treatment, cornea-protecting materials (corneal bandages) or controlled drug release contact lenses, which comprise, as their main component, a glycosaminoglycan (mucopolysaccharide) existing in the living body as an extracellular matrix component of connective tissues and the like, and satisfy various requirements such as dimentional stability, transparency, surface wettability, tissue compatibility (non-irritation, safety), oxygen permeability and the like.